Devices for cleaning the walls of boreholes



June 12, 1962 ATKINSON 3,038,540

DEVICES FOR CLEANING THE WALLS OF BOREHOLES 8 hmj Filed NOV. 29. 1957Claims priority, application Great Britain Dec. 5, 1956 11 Claims. (Cl.166-470) This invention relates to devices for cleaning the walls ofbore holes of the kind comprising spring wires or fingers carried uponsupporting means adapted to be mounted on the outside of a bore holecasing with the fingers extending outwardly with respect thereto andbeing shaped and arranged so that by reciprocating or rotating thecasing in the hole the springs or fingers exert a scratching actionwhich cleans the wall by removal of caked mud and the like. It is knownfrom my US. Patent No. 2,714,424 to provide a cleaning device in whichthe fingers are formed by bundled or stranded wires and each bundle orstrand is provided with one or more encircling metal sleeves or thimbleswhich are suitably angled to impart 'a desired directional set to thewire fingers as well as clamping the individual wires firmly together.In such constructions the resilience or ability of the fingers to returnto their initial position after having been deflected is restricted bythe clamping action of the angled sleeves or thimbles. Also it is knownfrom my US. Patent No. 2,787,328 to provide a device in which thefingers are formed from closely coiled helices of spring wire or thelike having one or more inserts or cores which occupy a part only of thelength of each finger whereby the fingers are maintained in the desiredshape or set. With such a construction the overall flexibility .of thefingers is reduced since bending can take place only between the insertsorcores. It is the object of the present invention to provide animproved form of spring finger which afi'ords the required stiffnesswhilst being flexible over the whole of its efiective length, willmaintain a desired set or shape, and also possesses the required abilityto return to its initial position and shape after having been deflectedduring the cleaning operation.

According to the invention ,a spring finger for the purpose describedconsists in a resilient multiple wire core within a sheath consisting ofa substantially close coiled wire helix, i.e. a helix having itsadjacent turns juxtaposed in mutually supporting relation to each otherthroughout at least the major part of its extent as herein shown, thefinger being shaped or set to the desired form for mounting. Theaforesaid sheath extends over at least the greater part of the length ofthe finger and if desired its ends may be flush with the ends of thecore.

According to a further feature of the invention the fitting between thewire core and the coil sheath is such that the wires of the core areenabled to slide relatively to one another to a certain extent when thefinger is deflected and such relative movement can also take place inthe region or regions whether the finger is angled or set. Thisarrangement afiords flexibility over the whole of the projecting oreffective length of the fingers.

According to a further feature of the invention the wire coil sheath isformed from resilient wire such as steel piano wire or tempered springwire so that it constitutes a helical spring. In this way the sheathincreases the stifiness of the finger and when deflection takes place atthe angled or set portions therefore the wire sheath will lengthen understrain and thereby enhance the ability of the finger to return to itsoriginal position after the deflecting force has been removed.

In the accompanying drawing,

FIGURE 1 is a side elevation, partly broken away, of

a spring finger constructed in accordance with the invention;

FIGURE 2 is a sectional end elevation of FIGURE 1;

FIGURE 3 is an end view of one of the ends of the finger of FIGURE 1;

FIGURE 4 is a sectional end elevation of amodified construction of thefinger;

FIGURE 4a is a detail of a modification of FIG. 4;

FIGURE 5 is an outside end elevation of another modified construction ofthe finger;

FIGURE 6 is a cross section on the line -XX of FIG- URE 5.

In carrying the invention into effect according to one convenient modeas shown in FIGURES 1, 2 and 3, there is provided a double finger ofU-shape comprising a pair of limbs 1 and 2 and a curved connecting endportion 3 which is shaped and adapted to be secured in any convenientmanner to a carrier (C, FIG. 4) which can in turn be secured to a borehole casing. The double finger is angled or set at two regions indicatedat 4 and 5 in FIGURE 2, thereby providing finger portions 6 whichproject outwardly from the bore hole casing (not shown) and have attheir ends further angled portions 7 directed either inwardly oroutwardly to assist in the scraping action. It will be understood thatthe portion of the U- shaped double finger from the point designated 4in FIG. 2 to the lower or recurved end of the latter, constitutes amounting portion, whereby the scratcher element may be secured to acarrier. The double or twin finger comprises a suitable length ofmultiple wire core 8, the wires being laid substantially parallel andconsisting of tempered spring steel wire or steel piano wire, a suitablewire size being 20 S.W.G. Preferably the wires are grouped about acenter wire as shown for example in FIGURE 3 where seven wires areemployed. A sheath surrounds the core 8 and consists of a close helicalcoil 9 of resilient wire of a gauge preferably greater than that of thecore wires. This wire sheath is wound over the core wires either beforeor after the fingers are formed to the desired shape. The winding is socontrolled that the fit between the core and the sheath will allow somerelative slip or creepage of the core wires at the angled regions 4 and5 of the finger when the latter is deflected. The wound and shapedfinger is suitably tempered to afford the desired degree of resilience.The ends of the core 3 are flush with the ends of the sheath 9.

In a modified form of finger as shown in FIGURE 4, the ends of the core8 protrude at 10 beyond the end of the sheath 9. The core ends 10 maylie parallel as illustrated or alternatively the individual core wiresmay be separated or splayed, as exemplified at 1011, FIG. 4a.

In a modified construction of finger as shown in FIG- URES 5 and 6, thecoil sheath is discontinued for a suitable distance between the angledregions 4 and 5 to expose the core at 11, leaving a relatively shortlength of sheath 12 extending on both sides of the angled portion orkink 5. To prevent the possibility of the sheath portion 12 turning oreven being pulled off during use two or three of the intermediate coilsare deformed to an oval shape as shown at 13 in FIGURES 5 and 6, therebyspreading the core wires to an elongated section.

It will be understood that twin finger elements as described above maybe mounted in any convenient or desired way upon a carrier (C, FIG. 4)which is adapted to be secured to the bore hole casing. Such carrier maycomprise a closed ring or may consist of separate elements preferably ofchannel form secured to the casing as by welding. In a convenientarrangement, the U-shaped end of the twin finger is secured by means ofa cleat or cover plate C suitably shaped to fit over said U-shaped endto be welded or otherwise secured to the carrier C. Preferably thefingers are mounted in such a manner that they are inclined with respectto the longitudinal axis of the casing. Such carriers are well known inthe art and are particularly illustrated in my Patent No. 2,787,328referred to above. It will also be understood that the twin fingerelements may have a narrow or a wide formation i.e. the substantiallyparallel finger portions may be relatively widely or closely spaced asmay be desired. However, the detailed shape of the wire fingers mayobviously be widely varied and the invention is not limited to theU-shaped finger construction.

It will be appreciated that spring fingers constructed in accordancewith the present invention are of larger diameter than those generallyemployed which in many instances consist of short single wires of about.072" in diameter. In this invention the fingers may be about A indiameter and such fingers are well adapted to remove soft caked mud fromthe bore hole, thereby exposing the harder layers beneath to the actionof the circulating fluid and permitting the progressive removal of suchlayers. This action is especially advantageous when cementing boreholes, and cleaning devices or scratchers according to the presentinvention are particularly well adapted for use in such circumstances.

I claim:

1. A well bore scratching device comprising, in combination, a carrierformed for mounting on a cylindrical casing to be run into a well bore,and a scratching finger having a mounting portion secured to saidcarrier and a portion projecting from said mounting portion andterminating in a free end displaced radially outwardly with respect tosaid formed carrier for engagement with the well bore, said fingercomprising a resilient multiple Wire core, said core being made up of aplurality of wires lying in generally parallel longitudinal contactingrelationship, and a resilient sheath closely disposed about said core,said sheath being in the form of a helical spring having its adjacentturns juxtaposed in mutually supporting relation to each otherthroughout at least the major part of its extent, and said sheathloosely clasping said core wires so that said core wires are freelocally to move longitudinally relative to said sheath and to each otherduring flexing of said finger.

2. The combination of claim 1, said core wires and resilient sheathbeing substantially co-terminous at their free ends.

3. The combination of claim 1, said core wires projecting beyond saidresilient sheath at their free ends.

4. The combination of claim 1, said sheath and core being bent centrallyof the length of said finger to constitute a U-shaped mounting portionand two free end portions projecting from opposite ends of said mountingportion and lying in spaced relation to each other, said U-shapedmounting portion being secured in said carrier.

5. The combination of claim 1, said core wires being bent at an angleWithin said resilient sheath at a region spaced from said mountingportion.

6. The combination of claim 5, said resilient sheath including a numberof coils of elliptical form embracing said core wire at said angularlybent regions.

7. A well bore wall scratcher finger having a U-shaped configurationcomprising a bight and two mutually spaced legs extending in the samegeneral direction from the respective ends of said bight, said bightconstituting a mounting portion for mounting said finger upon a supportfor attachment to a well pipe, said finger comprising an elongated coreof said U-shaped configuration made up of a plurality of generallyparallel individual wires each of said configuration, and a resilientsheath closely disposed about said core, said sheath being in the formof a helical spring having its adjacent turns juxtaposed in mutuallysupporting relation to each other throughout at least the major part ofits extent, and said sheath loosely clasping said core wires so thatsaid core wires are free locally to move longitudinally relative to saidsheath and to each other during flexing of said finger.

8. The combination of claim 7, said wires and sheath being substantiallyco-terminous at the ends thereof remote from said mounting portion.

9. The combination of claim 7, said wires projecting beyond said sheathat the ends thereof remote from said mounting portion.

10. The combination of claim 7, said wires being bent at an angle at aregion Within said sheath and in spaced relation to said mountingportion.

11. The combination of claim 10, said sheath including a number of coilsof elliptical form embracing said core Wires at said angularly bentregion.

References Cited in the file of this patent UNITED STATES PATENTS2,040,689 Duhain May 12, 1936 2,215,514 MacGregor Sept. 24, 19402,325,629 Peterson Aug. 3, 1943 2,421,647 Peterson June 3, 19472,634,813 Wright Apr. 14, 1953 2,714,424 Atkinson Aug. 2, 1955 2,787,328Atkinson Apr. 2, 1957

